Tubular skylights have been provided for illuminating rooms inside buildings with natural light. Not only do tubular skylights thus save electricity and, concomitantly, are environmentally benign, but they illuminate rooms in a pleasing way using natural sunlight instead of 60 cycle electric light. An example of a commercially successful tubular skylight is disclosed in U.S. Pat. No. 5,099,622, assigned to the same assignee as the present invention and incorporated herein by reference.
A tubular skylight includes a roof-mounted, dome-like transparent cover. The cover is mounted on the roof of a building by means of a flashing. An internally reflective tube depends downwardly from the roof to the ceiling of the room sought to be illuminated, and the bottom of the tube is covered with a light diffuser that is positioned at the ceiling.
In most existing tubular skylights, the ceiling dry wall supports the diffuser and the tube. This is so in part because existing tubular skylights are not designed to be installed during construction of the building, but rather are retrofitted into the building after construction, when the ceiling dry wall has been attached to the ceiling joists and, hence, when access to the void between the roof and ceiling may not be possible. In other words, the only practical way to mount the diffuser and lower end of the tube in many circumstances is to attach the tube to the ceiling dry wall, instead of to relatively sturdier but inaccessible ceiling joists above the dry wall. Accordingly, to install a tubular skylight, a hole must be cut in the existing ceiling dry wall and in the roof, and then the skylight positioned and mounted as described above.
While effective for retrofitting skylights into existing homes, the above-described installation technique is unacceptable in the context of new home construction. This is because many municipal codes require inspection of structures between the roof and ceiling. As intimated above, however, once the ceiling dry wall is attached to the ceiling joists, such inspection might be impractical to undertake. The present invention, however, recognizes that it is possible to provide a skylight that conveniently can be installed during new home construction to permit inspection of the skylight before the ceiling dry wall is installed.
Additionally, the present invention recognizes and addresses several other considerations in tubular skylight design. One such consideration is that both the diffuser and the cover be effectively sealed to the tube. Otherwise, water vapor can enter the tube and condense, thereby reducing the illuminating capability of the skylight. As recognized by the present invention, however, many existing cover seals are rendered ineffective because the tube tends to warp over time, thereby spacing the seal from either the tube or the cover.
Furthermore, it is desirable not only to provide an effective seal between the cover and the upper end of the tube, but it is also desirable to maintain a predetermined space between the flashing and the tube. This is because the flashing can be made from a metal that is different from the metal of the tube, and if the two dissimilar metals come into contact with each other, galvanic corrosion undesirably can be induced. In addition, providing a thermal barrier between the flashing and the tube is desirable to reduce heat transfer between the flashing and tube and, thus, to reduce the amount of energy required to heat or cool the building. As recognized by the present invention, both an effective seal and a spacer can be provided using a single component.
Still further, the present invention recognizes that thermal stress can cause the tube to move relative to the building, and that such movement can further reduce the integrity of the skylight assembly. And, the present invention understands that it might be desirable that a tube of a skylight be vertically adjustable relative to the building to facilitate installation of the skylight.
Accordingly, it is an object of the present invention to provide a tubular skylight that can be installed in a building during construction of the building. Another object of the present invention is to provide a tubular skylight that incorporates an effective seal between the roof cover and the tube, and that maintains a space between a roof flashing and the tube to reduce galvanic corrosion. Still another object of the present invention is to provide a tubular skylight that absorbs thermal stress. Yet another object of the present invention is to provide a tubular skylight that can be vertically adjusted relative to a building after the tube of the skylight has been attached to the building, to facilitate installation of the skylight. Another object of the present invention is to provide a tubular skylight that is easy to use and cost-effective to manufacture.